Micro-optical electromechanical system (MEOMS) membranes are used in a spectrum of optical applications. For example, they can be coated to be reflective and then paired with a stationary mirror to form a tunable Fabry-Perot (FP) cavity/filter. They can also be used as stand-alone reflective components to define the end of a laser cavity, for example.
Typically, membrane deflection is achieved by applying a voltage between the membrane and a fixed electrode. Electrostatic attraction moves the membrane in the direction of the fixed electrode as a function of the applied voltage. This results in changes in the reflector separation of the FP filter or cavity length in the case of a laser.
In optical systems, these membranes have advantages over cantilevered structures, for example. Membranes better maintain parallelism through the range of their deflection and tend to be more mechanically robust and have fewer relevant vibration modes.
In the past, the commercial MEOMS membranes have been produced by depositing a dielectric mirror structure over a sacrificial layer, which has been deposited on a support structure. This sacrificial layer is subsequently etched away to produce a suspended membrane structure in a release process. If a curved membrane structure is desirable, a compressive stress is cultivated in the silicon compound to induce a bow.